THE FIGURE OF THE EARTH 



17 



seas, are accounted for. The V-shaped continent extensions 

 and the A-shaped oceans of the southern hemisphere (Fig. 2) may 

 likewise be considered as relics of the now largely submerged tet- 

 rahedron of the southern hemisphere, since this had its apex to the 

 northward (Fig. 6). 



Thus we see that the lithosphere can scarcely be regarded as a 

 perfect spheroid, since in the course of geologic ages it has under- 

 gone successive de- t B 



partures from this 

 original form. In 

 its present state it 

 has been described 

 as tetrahedral, 

 though we must 

 keep in mind that 

 the sharp angles 

 of that figure are 

 deeply truncated. 

 The soundings 

 first by Nansen 

 and more recently 

 by Peary in the 

 Arctic basin, far 

 to the north of the 

 continental bor- 

 der, showed that this depression is characterized by profound 

 depths, and so have afforded confirmation of the tetrahedral fig- 

 ure. To match this depression at the northern extremity of the 

 earth's axis, a high continent reaching to elevations in excess of 

 10,000 feet has been penetrated by Sir Ernest Shackleton at the 

 opposite extremity of this polar diameter. Considering its size 

 and its elevation, the Antarctic continent with its glacier mantle 

 is the largest protuberance upon the surface of the lithosphere. 



In our study of the departures of the earth from the standard 

 spheroidal surface, we might even go a step farther and show how 

 the tetrahedron, which best represents the symmetry of the present 

 figure, is somewhat deformed by a flattening perpendicular to the 

 Pacific Ocean. To draw attention to this flattening of the earth, 

 it has sometimes been described as " potato-shaped," since the 

 c 



Faces tv/'r/t Apex fo 



FIG. 6. Diagrams for comparison of shore lines upon 

 tetrahedrons which have an angle, the first at the south 

 and the second at the north. 



